The objective of the proposed research is clarification of the fine structural mechanisms (1) by which commonly used substances, such as detergents and lipid solvents, injure the epidermis and become primary irritants, and (2) by which the skin repairs itself. Methods used will be transmission and scanning electron microscopy, histochemistry and autoradiography, both on light and electron- microscopic level. Tritium labeled irritants (e.g.kerosene) will be used to study penetration and localization of the substance, and tritium labeled thymidine and amino acids will be employed in rabbit skin to study synthesis of DNA proteins. On the basis of these data, the relative effectiveness of various protective agents will be determined in order to devise better methods of protection and treatment.